c - Is `y = x = x + 1;` undefined behavior? -

as title says, is

y = x = x + 1; 

undefined behavior in c?

answer question
no.

what happen
happen:

int x = 1; /* assume */ y = x = x + 1;  /* results: */ y == 2; x == 2; 

how compiles
same as:

x += 1; y = x; 

why not undefined
because not writing x in same expression read it. set + 1, assign y value of x.

your future
if find code confusing can use parentheses readability:

y = x = (x + 1);